Tactile Human Interface with Weight Supporting Lower Limb Exoskeleton

The paper describes conceptual design and control a new fully autonomous lower limb exoskeleton system by using a number of tactile sensors. The aim of the exoskeleton is to support a subject weight and provide an additional strength and endurance for the subject. The designed exoskeleton can decouple the weight/mass carrying function of the subject/human from its forward motion function. This newly proposed approach effectively reduces power and size of propulsion motors and thus overall weight, cost of the system. Interaction between the system and subject takes place by means of two types of sensors. The system measures the pressure applied by the subject's feet on the ground. If the pressure exceeds the set value the system blocks the motion at the knee joint by means of a passive air cylinder across the knee joint. The measured data is used by PID controller to force the exoskeleton to follow precisely the actual motion of the subject legs while swinging. Controller does it by means of hip and knee motors. The mechanical structure of each leg has six degrees of freedom: four at the hip, one at the knee and one at the ankle. Only one degree at the hip and one at the knee are motor driven. This exoskeleton is a power efficient because the exoskeleton motors are not used support the subject weight like in most of the existing exoskeleton designs.